1. Field of the Invention
The present invention relates to a high cellulose type coated electrode to be used for the downward butt welding of fixed pipes.
2. Description of the Prior Art
A high cellulose type coated electrode is suitable for downward welding because of its great arc force and its slag formation in small quantities. In addition, it facilitates melt-through welding on account of its arc characteristics. These features permit an extremely high welding speed for root pass in the downward butt welding of fixed pipes. For this reason, it has long been accepted for the site welding of pipe line in Europe and America.
However, a high cellulose type coated electrode has a disadvantage that it cannot be used for the welding of pipe line in cold districts where low-temperature toughness is important. This disadvantage is due to the fact that a high cellulose type coated electrode contains very little shielding material such as carbonate and fluoride and hence gives rise to weld metal containing oxygen and carbon (originating from cellulose) in large quantities which lead to a low toughness. Therefore, welding in cold districts needed a low hydrogen type coated electrode which is by far inferior in performance to a high cellulose type coated electrode.